Genetic systems in the south-west flora: implications for conservation strategies for Australian plant species

Abstract

Is genetic diversity a reliable indicator of evolutionary capability? A
comparative study of genetic systems in Australian native plants, particularly
from south-west Australia, suggests the primitive condition to be
recombinationally capable with low allelic diversity. Diversity has
accumulated in some nursery lineages in association with lethal equivalent
polymorphisms. This generated an elevated evolutionary capability which
allowed escape from the benign nursery into the demanding arid playground.
Lethal equivalent polymorphisms also generate a high genetic load which drives
genetic system evolution towards the minimisation of that load. Many of the
devices which reduce the genetic load, including chiasma localisation at
meiosis and reduced chromosome numbers, are impedimenta to recombination and
they must reduce evolutionary capability. Thus, to correctly interpret the
levels and patterns of genetic diversity within an Australian plant population
system we need to know how its genetic system operates and how much it is
recombinationally impeded. It may be true that in many Australian plant
population systems, the more genetic diversity we see, the less evolutionary
potential there is. Conservation strategies based on a misunderstanding of the
relevance of genetic diversity in population systems may be quite disastrous.